Probabilistic strength of {111} n-type silicon

The two-parameter Weibull strength distribution of {1 1 1} n-type silicon p rismatic bars was determined in four-point bending and analyzed as a functi on of specimen size (width), loading rate, two different crystallographic o rientations, and specimen orientation (polished or etched surface in tensio n). 100% fractography was performed to classify strength-limiting flaw type s and to censor the strength data. All flaw types were extrinsic. Machining or cutting damage in the form of chipped edges (an edge-type flaw) was the dominant strength-limiting flaw when the polished surface was subjected to tensile stress, while a flat-bottomed etch pit (a surface-type flaw) was t he dominant strength-limiting flaw when the etched surface was subjected to tensile stress. The censored Weibull strength distribution was independent of specimen width, loading rate (indicative of slow crack growth insuscept ibility), and the two crystallographic orientations; however, it was depend ent on specimen orientation. Pooling of the strength data was employed to t ighten the confidence intervals about the censored parameters. The results from this study indicate that different extrinsic strength-limiting flaws a nd strength distributions will be operative depending on the manner in whic h a silicon component is stressed.